We have continued to develop and extend the usefulness of our new technique for measuring IgG Fc receptors and complement receptors in various groups of patients with autoimmune disease. These techniques have proven useful both in diagnostic tests and for developing a further understanding of pathophysiologic processes. In the past year we have extended our studies to patients with mixed IgM, IgG cryoglobulins and have shown that these patients can be divided into two groups. The patients with Fc receptor defects are the ones who develop immune complex mediated renal disease. The patients with normal Fc receptor function do not appear to develop immune complex mediated renal disease. The follow-up studies have been performed in our patients with lupus erythematosus and it has been shown that as the patients improve the immune clearance defect also improves. Patients with mixed connective tissue disease have been studied and have been shown in general to be free of defects in immune clearance notwithstanding the fact that they have circulating immune complexes. This is in keeping with previous observations that these patients do not develop immune complex mediated tissue injury.